The relationship between surface sediment diatom assemblages and pH in 33 Galloway lakes: Some regression models for reconstructing pH and their application to sediment cores

The species composition of surface sediment diatom assemblages in 33 Galloway lakes, pH range c. 4.5 to 7.4, is related in a statistically significant manner to water acidity (or to factors closely associated with pH). Predictive models of summer mean pH, using simple regression equations of Index B (Renberg & Hellberg, 1982) with both Scandinavian and Galloway data sets, and multiple regression equations using diatom pH preference groups and individual species, are described and applied to fossil diatoms in six sediment cores. Although multiple regression of individual species gives the highest correlation coefficient (r²=0.87) in the modern data set this method is least appropriate for reconstructing pH values from fossil material where predictor species are often absent. Of the four methods examined here it is suggested that multiple regression of diatom preference groups is probably the most suitable for pH reconstructions from sediment cores.     

Transplant experiments. Growth-limiting factors for diatoms and bluegreen algae in Norwegian lakes

Population densities and total phosphorus concentrations in samples from different lakes of south-eastern Norway were determined. In addition some transplant experiments with dilute phytoplankton populations were carried out. A laboratory batch culture method was used.The diatoms studied may be divided into three ecological groups based on their cell densities and total phosphorus concentrations in the samples. This classification was supported by the experimental results. Cyclotella spp., Asterionella formosa and Tabellaria fenestrata did not grow or had low growth rates above pH 9. Synedra cf. acus and Fragilaria crontonensis had often high growth rates within the pH 9–10 range, but were not able to grow at pH values above 10. High pH-values had no effect on the growth rate of Oscillatoria. Oscillatoria, Synedra and Stephanodiscus were severely growth-limited in filtered water from oligotrophic lakes. Maximum growth rates of all the populations studied were often obtained after addition of phosphate and chelated iron (FeEDTA) in combination to filtered water samples from oligotrophic/mesotrophic lakes.     

蟾蜍卵母细胞的Na~+/H~+交换

应用pH选择性徽电极和普通檄电极测量了蟾蜍卵母细胞内的pH值(pHi)。当用含NH_4~+而不含HCO_3~-的溶液培灌卵母细胞时,pHi逐渐下降,在停止培灌后,pHi恢复到对照值。这个pHi恢复过程是一个H~+的主动转运,用胆碱离子取代培灌液中的Na~+可以抑制pHi的恢复,这种抑制作用是可逆的。伴随着细胞内pH值的恢复,细胞内Na~+活度(Na_1~+)呈现暂时性增加,而细胞内Cl-活度(Cl_1~+)不变或稍有增加。实验结果提示在蟾蜍卵母细胞膜上存在着Na~+/H~+的交换。     

Lowering of pH does not directly affect the junctional resistance of crayfish lateral axons

Summary The effect of pH was tested on the junction between crayfish lateral axons. By means of a glass capillary inserted into one of the axons, one side of the nunction was perfused with solutions of known pH while the junctional resistance,R _j, was monitored. Integrity of the gap junction was checked electron microscopically.R _j remained unchanged when the pH of the perfusate was lowered from 7.1 to 6.0. However, when the pH of the unperfused side of the junction was lowered by substituting acetate for chloride in the external solution,R _j rose, attesting to the integrity of the junction and its capacity to uncouple in the perfused state. We suggest that H⁺ does not affect the junctional channels directly, but acts through an intermediary which is inactivated or removed by the perfusion.     

Regulation of intracellular pH in LLC-PK1 cells by Na+/H+ exchange

Summary Suspensions of LLC-PK₁ cells (a continuous epitheliod cell line with renal characteristics) are examined for mechanisms of intracellular pH regulation using the fluorescent probe BCECF. Initial experiments determine suitable calibration procedures for use of the BCECF fluorescent signal. They also determine that the cell suspension contains cells which (after 4 hr in suspension) have Na⁺ and K⁺ gradients comparable to those of cells in monolayer culture. The steady-state intracellular pH (7.05±0.01,n=5) of cells which have recovered in (pH 7.4) Na⁺-containing medium is not affected over several minutes by addition of 100 M amiloride or removal of extracellular Na⁺ (Na _o ⁺ /H _i ⁺ and Na _i ⁺ /H _o ⁺ exchange reactions are functionally inactive (compared to cellular buffering capacity). In contrast, Na _o ⁺ /H _i ⁺ exchange is activated by an increased cellular acid load. This activation may be observed directly either as a stimulation of net H⁺ efflux or net Na⁺ influx with decreasing intracellular pH. The extrapolation of this latter data suggests a set point of Na⁺/H⁺ exchange of approximately pH 7.0, consistent with the observed resting intracellular pH of approximately 7.05.     

Dihydrotetrabenazine Binding and Monoamine Uptake in Mouse Brain Regions

The objective of the present study was to estimate extracellular pH (pHe) and intracellular pH (pHi) during near-complete forebrain ischemia in the rat, and to evaluate the relative importance of lactic acidosis and rise in tissue Pco2 (Ptco2) in causing pHe and pHi to fall. The animals, which were ventilated, normoxic, normocapnic, and normothermic, were subjected to 15 min of ischemia, either without or with 30-60 min of recirculation. Ptco2 was measured with a tissue electrode, pHe with a double-barrel liquid ion-exchanger microelectrode, changes in extracellular fluid (ECF) volume by impedance measurements, tissue CO2 content by a microdiffusion technique, and labile tissue metabolites by enzymatic fluorometric methods. Ischemia caused Ptco2 to rise to between 95 and 190 mm Hg (mean 149 mm Hg), and pHe to fall by 0.45-1.05 units (mean 0.70 units). During recovery, Ptco2 normalized within 5 min and pHe after 15-30 min. During ischemia, high-energy phosphates were depleted and tissue lactate content increased to 15 mumol X g-1. The total CO2 content (Tco2) was minimally or moderately reduced (normal, 11.9 mumol X g-1; range of ischemic values, 7.9-12.1 mumol X g-1), this range probably reflecting variable amounts of remaining blood flow. Impedance measurements demonstrated that ECF volume during ischemia was reduced to 55% of control, with gradual normalization during the first 15-30 min of recirculation. From values for Ptco2, Tco2, [HCO3-]e, and ECF volume, [HCO3-]i and pHi could be calculated. These values pertain to an idealized homogeneous intracellular compartment, and the methods used cannot detect whether different intracellular compartments diverge in their acid-base responses.(ABSTRACT TRUNCATED AT 250 WORDS)     

Influence de pH acides sur la viabilité d'isolats deFrankia

Résumé Vingt souches deFrankia, isolées à partir de 7 espèces différentes de plantes actinorhiziennes ont été cultivées sur des milieux maintenus à des pH constants de 5; 4,8; 4,6 et 4,2. Chaque souche a été cultivée 2 à 3 fois consécutives à un même pH. Quatorze souches ne montrent aucune croissance à pH 5. Seules 3 souches résistent à un séjour de plusieurs semaines à pH 4,6. Aucune souche ne demeure viable après un séjour dans un milieu à pH 4,2. Les 3 souches acido-résistantes supportent également la présence d'Al⁺⁺⁺ libre dans le milieu de culture. Une forte concentration d'H⁺ dans le milieu stimule beaucoup la sporogénèse. Inoculée dans un sol acide une souche acido-résistante conserve une chance de survie nettement supérieure à celle d'une souche neutrophile maintenue dans les mêmes conditions.      

叶绿素寡聚体的光化学性质及其水悬浮液在光下的pH变化

单体叶绿素α在含水的石油醚中形成叶绿素α-水寡聚体,在含二氧六圜的石油醚中形成叶绿素α-二氧六圜寡聚体。两者除吸收光谱有所不同外,其光化学性质也有明显区别:叶绿素α-二氧六圜寡聚体的延迟发光强度比叶绿素α-水寡聚体的大一个数量级;叶绿素α-二氧六圜寡聚体带有负电荷,电镀时趋向正极,叶绿素α-水寡聚体带正电荷,电镀时趋向负极;两种寡聚体电镀所成的膜在光下产生相反的光电位。叶绿素α-水寡聚体水悬浮液在照光时有pH值变化,变化幅度0.2—0.3pH单位,停止照光pH恢复原值。     

Transformation and growth related changes in levels of nuclear and cytoplasmic proteins antigenically related to mammalian beta-galactoside-binding lectin

Immunofluorescence and immunoblotting experiments, using a monoclonal antibody to the 13 kDa mammalian beta-galactoside-binding lectin have shown that human lymphocytes contain nuclear and cytoplasmic proteins of apparent molecular masses of 130, 80, 65 and 13 kDa that are antigenically related to the lectin and whose levels and patterns of expression change in association with transformation, or after stimulation with mitogens. These observations, together with the finding that the myeloid cell line K562 is also rich in the 130 kDa component, whereas the mature granulocytes of normal donors and of patients with chronic myeloid leukaemia are lacking in all of the immunoreactive forms, raise the possibility that this family of lectin-related proteins may be components of growth regulatory systems that are variously elicited in the transformed and stimulated cells.